Photographic lens.



PATENTED APB. 5, 1904 2 SHEETS-SHEET 1 I i E i g I FQ l F if um, ilm YLG. n 1/ N1 ..4 Y mmm n@ m W LPM N Mmm a M. x n www m TA- Low. HL |l||l||| m, R9. Pn L SU x I m l M .M l 1|` /N E N N ,N l N. 7 R 0 7 m N J 5 u u D d 1 l i I Draflslnlla No. 756,779. PATENTED APR. 5, 1904.

I T. R. DALLMEYER.

PHOTOGBAPHIG LENS.. urmourol man Dnc. 1s, ma. no xonnr..

2 SHEETS-SHEET 2.

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UNITED STATES Patented Aprii' e, 1904.".-Y

PATENT OFFICE.

PHOTOGRAPHIC LENS.

SPECIFICATION forming part of Letters Patent N0. 756,779, dated April 5, 1904.

Application filed December 18, 1899. Serial No. 740.776. (No model.)

To all whom, t may concern,.-

Be it known that I, THOMAS RUDoLrHUs DALLMEYER, optician, a subject of the Queen of Great Britain, residing at Newman street,

5 Oxford street, in the county of Middlesex,

England, have invented certain new and useful Improvements in Photographic Lenses, of which the following is a specification.

The object of this invention is to provide IO as an adjunct to any ordinary photographic lens which is complete in itself an optical rneansfvincreaslng the size of the image *formed by tne lens withogt necessarily dimlnisling the intensity ofthlilliirnlnatlon. i

I5 Throughout the specification I employ the term lens as including compound lenses or lens systems; but the term system excludes a single lens.

In all optical systems hitherto constructed for photographic purposes direct enlargement if the image has been brought about as folows:

A. By primary magnification, in which case a converging lens is combined with a di- 2; verging lens, forming what is known as a telephotographic lens. The image is direct and inverted, its illumination being decreased in proportion to the area of the enlarged image as compared to that given by the converging lens alone-that is to say, as the square of the linear magnification.

B. By secondary magnilication, in which the primary inverted image formed by an ordinary converging lens is subjected to enlargement by a second converging lens, reinverting the image and' forming an erect enlarged image. Here again the illumination of the latter is decreased in proportion to the square of the linear magnification.

In both cases it has hitherto been customar\T to employ a converging lens of given initial intensity as a basis for subsequent conversion into an enlarging system by the addition of a posterior enlarging system as described under paragraphs A or B, where the initial intensity of the converging lens rapidly diminishes with the degree of enlargement.

My invention consists in an adjunct or ad.- dition of an optical enlarging system to the anterior portion of any complete photographic lens, whereby, first, I avoid the proportionate loss of illumination in the enlarged image necessitated by the old methods; second, I may even maintain the initial intensity given by the converging lens alone at its focal plane when the enlargement is not great.

My present object in particular is to assist the user of the hand-camera and the smaller sizes of cameras to avoid exaggerated perspective by enabling the operator to be at a greater distance from the foreground of his subject and yet maintain a suiiiciently large image, also to obtain by the addition of the enlarging system to his lens enlarged details in subjects of general interest included by the ordinary lens used alone, distant objects, &c. The invention may, nevertheless, be applied to any ordinary lens to attain the ends of a telephotographic system with greater mechanical convenience, the additional system t0 7 O screw into the place of the hood of the lens.

Figures 1, 2, and?) are diagrams illustrating one Way ofcarrying out my invention. Fig.

4 illustrates a modification. Figs. 5 and 6 show the combination of lenses without lines indicating the rays.

A is an ordinary photographic lens, and B and C are the lenses making up the enlarging system. B and C are mounted in tubes D and E, sliding one within the other, so that 8O the distances apart of B and C can be varied, as shown in Figs. l, 2, and 3. Fig. 4 is similarly constructed, but it has not been thought necessary to show more than one portion. The lens B should be of the high- 35 est intensity possible-that is to say, of the largest diameter and shortest focal length convenient, so that when combined with C for a given linear magnilication the initial intensity of the lens A, to which it is added, may be maintained or, at any rate, diminished in a less degree than would be the case with any posterior attachment to the original converging lens A. The lens C should be of shorter focal length than that of the lens A, again maintaining the largest diameter and shortest focal length possible, so as to maintain in combination with B the initial intensity for a given linear magnification when this is feasible. The power of the diverg-IOO 5 tion required, I decide the ratio of the focal length of B to that of C. When the lenses B and C are placed at the normal separation` that is, at a distance equal to the difference of their focal lengths, as shown in Fig'. 1-

I parallel rays incident upon B will after refraction at C emerge parallel. Now if we place this supplementary system in front of anyordinary lens A, which has been focused for parallel rays, (forming an image at F in I its focal plane,) it is obvious that the addition of this s stem, wli1ch transmits pa'rallel ra S w1 not a er e p e ocus, but W1 1ncrea r 1mens1ons of the image in a ratio equal to the ratio of the focal lengths 2O of- B and C. If the effective diameter of the aperture of the lensf4 B is greater than that of A, it is 'evident that the loss of illumination due=to magnification may be compensatedfor partially or entirely. -If thejratio of the effective diameters off B and A is equal to the ratio of 'the focal-lengths of'B and C, the illumination is identical. -If less, the illumination1 i'sdiminished, supposing always that the vfufllpencilof rays incident upon B is trans- '30 mittedby C, which canA be accomplished. If

the glenses composing thesupplementary sysy'temare brought nearertogether, as shown in: Fig. 2, it becomes a system of variable ldiverging focal length, 'transmitting divergent --v rays from any object tothe-lens A, thus permitting a still more enlarged image to'be received'lat Ff any distance beyond the focal plane of the lens A, depending upon the separation between-Bt and C for theV time being.

f4 If the lenses Band C are separated byany interval greater than the normal separation, as 1 shown in Fig. 3, it is obvious that it becomes a system of variable convergingfocal length.

Parallel incident rays upon the supplemen- 415: tary system now emerge convergent, causlng the image to be received upon a plane nearer to the lens AF-than its focal plane. In this =case it will :be seen that the linear magnificationwill beless than the. ratio'of the focal 5 O- lengths of B and C; but the illumination may be greater than that y.of the lens A used alone. With the ylenses separated, as in Fig. 3, it is evidentV that any near object may transmit parallel rays to-th`e lens A with an enlarged 554 imageat itsfocal plane.

f It -will be evident that near objects may be photographed with l B and C arranged as shown in'Fig. 2; but the plane'of the image must be `beyond the focal plane of the lens A.

.60 The lenses '-Band C are each preferably vaplanatic. `Thenformascribed to the lensB --Will determi-ne that to be ascribed to C.

Figs. 1, 2, and 3- illustrate one of many forms convenient for-carrying out the object ;of` this invention. f'lhe detailsI of the lenses are as follows: B is a cemented combination, 111511191381515, belng twice that of A or C.

H Dune Byline 13 i575 i tbicknessu" 1.6202 1.64.28 Rg; 33,. ithmkness .35 1.5170 1.5279

C is a symmetrical diverging combination with edges in contact. Diameter .75, equal to gat of A. Focal length equals half that of In the enlarging system illustrated in Fig. 4, B and C are both converging systems. If the image formed by the lens B, whether for parallel rays (as illustrated) or for a near object, (in which case B must be farther separated from C,) lie in the front focal plane of the lens C, then C will transmit parallel rays to the lensi A, and hence the final enlarged image will be received upon the focal plane of A. The image may, however, be received upon any plane nearer to or farther from the lens A than its focal plane by an adjustment of the separation of' B and C. If the image formed by B falls nearer to C than its focal plane, divergent' rays will be transmitted to the lens A. If the image formed by Bis farther removed froml C than its focalplane,Vv will transmit convergent rays` tothe lens A.

IOO

B and' C are each preferably aplanatic. Each forms an image independently of the other,

so that for this purpose' B and C may be any" two aplanatic systems whatsoever; but each should have the highest intensity attainable.

rEhe .following are the particulars of the lenses in Fig. 4. B is composed of two cemented combinations G and H.

u. for D line u-for l, l lHy line gig-48d thickness .1.5170 `1.5279 2- ihicknessl" k1.6202 1.6428

IH, diameter 1.: t f

l, Dt 1151.25.

thickness-2" .1.5170 1.5279 Rg, i ithiclmess-075 11.6202 1.6428

Fixed separation from Rs to Ra 1,- 21.' C is composedrof two cemented combinations J and K.

J, diameter .7 5:

, p. for a for D line .Hy line ogQ/l thickness .06 1.5170 1.527 9 Rgw., thickness .2 v1.6202 1.6428

IIO

K, diameter .85":

Fixedr separation from R1 to R10 1.05.

B is here twice the focal length of C and twice the diameter of A.

What I claim is- 1. The combination with an ordinary photographic lens complete in itself, of an enlarging system placed in front of it, and consisting of a front converging and a rear diverging ens.

2. The combination with an ordinary photographic lens complete in itself, of an enlarging system placed infront of it, and consisting of a front converging and a rear diverging lens, and means for varying the distance apart zo of these two lenses.

3. The combination with an ordinary photographic lens complete in itself, of an enlarging system placed in front of it, and consisting of a front converging and rear diverging 2 5 lens., the system being such that parallel incident ra s einer e arallel "1, Iiie combination with an ordinary photographic lens complete in itself, of an enlarging system placed in front of it, and consisting of a front converging and a rear diverging lens, and means for varying the distance apart of these two lenses, the system being such that parallel incident rays einer e n s 5. v e com 1 n: ion w1 an ordinary photographic lens complete in itself, of an enlarging system placed in front of it, and consisting of a front converging andarear diverging lens, the diameter of the converging lens being greater than those of the diverging and photographic lenses.

6. rl`he combination with an ordinary photographic lens complete in itself, of an enlarglio ing system placed in front of it, and consistof these two lenses, the diameter of the con-'- verging lens being greater than those of the tographic lens complete in itself, of an enlarg-` lens, and means for varyingthe distance apart ing system placed in front of it, and consisting of a front converging and a rear diverging lens, the system being such that parallel incident rays emerge parallel, the diameter of the converging lens being greater that those of the diverging and photographic lenses.

8. The combination with an ordinary photographic lens complete in itself` of an enlarging system placed in front of it, and consisting of a front converging and a rear diverging lens, and means for varying the distance apart of these two lenses, the system being such thatl parallel incident rays emerge parallel, the diameter of the converging lens being greater than those of the diverging and photographic enses.

9. The combination with a photographic lens adapted to be focused as in the usual operation of a camera, of an adjustable enlarging system placed in front of it, and roducing at will different degrees of magnification of the l/jiage.

" image-enlarging device consisting of a front converging lens, and a rear diverging lens mounted in a suit-able tube or holder and adapted to be applied in front of the focusing-lens of an ordinary camera.

11. An image-enlarging device consisting of a front converging lens and a rear diverging lens mounted in a suitable holder, and adjustable, one with reference to the other, and adapted to be applied in front of the focusinglens of an ordinary camera.

THOMAS RUDOLPHUS DALLMEYER.

Witnesses:

(LJ. CROW,

ing of a front converging and a rear diverging G. Low. 

